Polycarbonates are well known and have been widely employed for the production of thermoplastic molded articles.
Polycarbonate derived from bisphenol-A is a high-performance plastic with good impact strength. In addition to ductility (impact strength), an article molded from general-purpose polycarbonate has high transparency, wide temperature limits (high impact resistance below -60.degree. C. and a UL thermal endurance rating of 115.degree. C. with impact), good dimensional stability, high creep resistance and electrical properties which qualify it as sole support for current carrying parts (up to 125.degree. C. without loss of impact strength).
Polycarbonate has low water absorption, good stain resistance and a wide range of colorability. However, polycarbonates have a relatively limited range of chemical resistance, which necessitates careful appraisal of applications involving contact with certain organic solvents, some detergents, strong alkali, certain fats, oils and greases.
It is reported in the prior art that mixtures of polycarbonates and organic fibers improve the flame resistance of polycarbonates. Thus, U.S. Pat. No. 4,061,691 describes a molding composition having improved flame-resistance containing polycarbonate and organic fibers, which include, inter alia, highly crystalline or highly heat distortion-resistant saturated thermoplastic polyesters such as poly(ethylene terephthalate), poly(butylene terephthalate) and poly(1,4-dimethylenecyclohexane terephthalate). However, the inclusion of these aforementioned polyester fibers generally tends to adversely affect the impact strength and transparency of these products as compared to polycarbonates which do not contain said polyester fibers.
Further, U.S. Pat. No. 4,056,504 describes polycarbonate molding resins with improved flow and strength properties which contain about 10 to 40 weight percent glass fibers and about 0.5 to 5 weight percent of polyalkylene glycol terephthalate or about 0.5 to 10 weight percent of polyalkylene glycol isophthalate. The presence of these aforedescribed polyesters generally, however, adversely affects the optical transparency of these polycarbonate compositions thereby making them generally unsuitable for many uses, such as windows and the like, where optical transparency and clarity are required. Furthermore, this patent discloses that the addition of larger amounts of polyalkylene-iso-phthalates detracts from the polycarbonate properties such as impact strength.